Catalyst composition, ammonia synthesis catalyst, and ammonia synthesis method

Abstract

Provided are: a catalyst composition with which high reaction activity can be obtained even in an activation treatment at a lower temperature; an ammonia synthesis catalyst; and an ammonia synthesis method using the same. A catalyst composition according to the present invention is characterized by containing the additive represented by formula (1) and the catalyst substance represented by formula (2).　Formula (1): AH2-x (In formula (1), A is a metal element containing at least one element selected from the group consisting of Zr and Mg, and x represents a numerical value where 0 ≤ x ≤ 2.)　Formula (2): MpOqCwNsHt (In formula (2), M represents one or more elements selected from the group consisting of the main-group elements and the transition elements, but where M does not simultaneously include aluminum (Al) and calcium (Ca), p represents a numerical value of 1 or more, q represents a numerical value of 0 or more, w represents a numerical value of 0 or more, s represents a numerical value of 0 or more, and t represents a numerical value of 0 or more. However, q, w, s, and t are not simultaneously 0.)

Description

Catalyst composition, ammonia synthesis catalyst, and ammonia synthesis method

[0001] This application claims priority to Japanese Patent Application No. 2024-084864, filed May 24, 2024, the contents of which are incorporated herein by reference.

[0002] Catalysts are often used to promote chemical reactions. One example of a chemical reaction is the ammonia synthesis reaction, which is a hydrogenation reaction. For example, a typical ammonia synthesis method is the Haber-Bosch process. The Haber-Bosch process uses Fe ３ O ４ A few mass % of Al ２ O ３ and K. ２ This method uses a doubly promoted iron catalyst containing O and directly reacts a mixed gas of nitrogen and hydrogen with this catalyst under high temperature and pressure conditions to produce ammonia. This technology is still used industrially today with the manufacturing process remaining almost unchanged since its completion.

[0003] Meanwhile, methods for synthesizing ammonia at temperatures lower than the reaction temperature of the Haber-Bosch process have been studied. Catalysts capable of synthesizing ammonia by contacting nitrogen and hydrogen have been studied, and transition metals have been studied as catalytically active components. Among these, a method in which ruthenium (Ru) is supported on various supports as a catalytically active component and used as an ammonia synthesis catalyst has been proposed as an efficient method (see, for example, Patent Document 1).

[0004] Furthermore, there is a demand for catalysts that are more active and more advantageous in terms of production costs, etc. The addition of activators to support metal catalysts to improve their reaction activity has been investigated. For example, Ti and TiH ２ It has been proposed that the activity of a Ru-based catalyst can be significantly improved by adding such an additive (for example, Patent Document 2).

[0005] Furthermore, studies are being conducted to improve catalyst activity by using Co or Fe, which are less active but relatively inexpensive, instead of Ru, which has high performance but is expensive, as a catalytically active component (see, for example, Patent Document 3).

[0006] JP 2006-231229 A International Publication No. 2023 / 085185 International Publication No. 2019 / 059190

[0007] The supported metal catalysts described in Patent Document 1 typically use a carbonaceous support such as activated carbon or an inorganic oxide support. However, these supported metal catalysts do not always have sufficient performance for practical use. Furthermore, ammonia synthesis catalysts using supported metal catalysts such as those described in Patent Documents 2 and 3 typically require a reduction treatment, such as heating in a hydrogen stream, to activate the catalyst before use in the reaction. However, this reduction treatment requires high temperatures of 600°C or higher. This not only entails energy-saving considerations during production, but also presents the problem of being unable to use the catalyst in the worst-case reaction due to material constraints on the reactor. Therefore, there is a need for an ammonia synthesis catalyst that can be activated at a lower temperature when a reduction treatment is performed and has high reaction activity.

[0008] The present inventors have discovered a catalyst composition, an ammonia synthesis catalyst, and an ammonia synthesis method using the same that can achieve high reaction activity even in activation treatment at lower temperatures by adding a specific additive, and have completed the present invention.

[0009] That is, the gist of the present invention is as follows: [1] A catalyst composition comprising an additive represented by the following formula (1) and a catalyst material represented by the following formula (2): AH ２－ｘ (1) (In formula (1), A is a metal element including at least one selected from the group consisting of Zr and Mg, and x is a value in the range of 0≦x≦2.) M ｐ O ｑ C ｗ N ｓ H ｔ(2) (In formula (2), M represents one or more elements selected from the group consisting of main group elements and transition elements, with the proviso that M does not contain aluminum (Al) and calcium (Ca) at the same time, p represents a value of 1 or more, q represents a value of 0 or more, w represents a value of 0 or more, s represents a value of 0 or more, and t represents a value of 0 or more, with the proviso that q, w, s, and t are not all 0 at the same time.) [2] The catalyst composition according to [1], wherein in formula (1), A represents at least one element selected from the group consisting of Zr and Mg. [3] The catalyst composition according to [1] or [2], wherein, in the formula (2), M represents one or more elements selected from the group consisting of barium (Ba), cerium (Ce), magnesium (Mg), calcium (Ca), strontium (Sr), lanthanum (La), silicon (Si), and aluminum (Al), p is a numerical value of 1 or more, q is a numerical value of 1 or more, w is a numerical value of 0 or more, s is a numerical value of 0 or more, and t is a numerical value of 0 or more. [4] The catalyst composition according to any one of [1] to [3], wherein the catalyst substance represented by the formula (2) is a catalyst substance represented by the following formula (2-1): M ｐ O ｑ (2-1) (In formula (2-1), M, p, and q have the same meanings as M, p, and q in formula (2)). [5] The catalytic substance is Ba—MgO, Sr—MgO, Ba—MgAl ２ O ４ , BaAl ２ O ４ , CeO ２ , Ba—CeO ２The catalyst composition according to any one of [1] to [4], wherein the additive is one selected from the group consisting of:

[0014] . [6] The catalyst composition according to any one of [1] to [5], further comprising a catalytically active metal. [7] The catalyst composition according to [6], wherein the catalytically active metal is at least one selected from the group consisting of ruthenium (Ru), cobalt (Co), iron (Fe), nickel (Ni), molybdenum (Mo), rhodium (Rh), rhenium (Re), chromium (Cr), and manganese (Mn). [8] The composition according to [7], wherein the catalytically active metal is cobalt (Co) or iron (Fe). [9] A method for producing the catalyst composition according to any one of [1] to [5], comprising: mixing the additive with the catalytic substance or a precursor thereof.

[10] A method for producing a catalyst composition according to any one of [6] to [8], comprising: a first step of mixing the catalytic substance or a precursor thereof with the catalytically active metal or a precursor thereof, a second step of reacting the first mixture obtained in the first step to cause the catalytically active metal to be supported on the catalytic substance, thereby obtaining a metal-supported material, and a third step of mixing the additive with the metal-supported material.

[11] An ammonia synthesis catalyst using the catalyst composition according to any one of [1] to [8].

[12] A method for producing ammonia, comprising a step of reacting nitrogen with hydrogen in the presence of the ammonia synthesis catalyst according to

[11] .

[0010] The present invention provides a catalyst composition, an ammonia synthesis catalyst, and an ammonia synthesis method using the same that can achieve high reaction activity even when activated at a lower temperature. The obtained catalyst also has high stability and high recyclability.

[0011] 1 is a graph showing the catalytic activity (ammonia synthesis rate) of the catalyst compositions (ammonia synthesis catalysts) of Examples 1 to 3 and Comparative Examples 1 to 8 (catalyst material: Co / Ba—MgO, pretreatment conditions: 450°C, reaction conditions: 400°C, 0.9 MPa). FIG. 2 is a graph showing the change over time in the catalytic activity (ammonia synthesis rate) of the catalyst compositions (ammonia synthesis catalysts) of Examples 1 and 2 (reaction conditions: 400°C, 0.9 MPa). FIG. 3 is a graph showing the change over time in the catalytic activity (ammonia synthesis rate) of the recycled catalysts of the catalyst compositions (ammonia synthesis catalysts) of Example 1 and Comparative Example 5 (after exposure to the atmosphere, no pretreatment, reaction conditions: 400°C, 0.9 MPa). FIG. 4 is a graph showing the temperature dependence of the catalytic activity (ammonia synthesis rate) of the catalyst compositions (ammonia synthesis catalysts) of Examples 1 and 2, Example 4, and Comparative Example 5 (pretreatment conditions: 450°C, reaction conditions: 200 to 400°C, 0.9 MPa). 1 is a graph showing the activation energy obtained from the temperature dependence of the catalytic activity (ammonia synthesis rate) of the catalyst compositions (ammonia synthesis catalysts) of Examples 1 and 2, Example 4, and Comparative Example 5 (pretreatment conditions: 450°C, reaction conditions: 200-400°C, 0.9 MPa). This is a graph showing the change before and after the ammonia synthesis reaction for the catalyst composition (ammonia synthesis catalyst) of Example 1 (reaction conditions: 400°C, 0.9 MPa). This is a graph showing the change before and after the ammonia synthesis reaction for the catalyst composition (ammonia synthesis catalyst) of Example 2 (reaction conditions: 400°C, 0.9 MPa). This is a graph showing the change before and after the ammonia synthesis reaction for the catalyst composition (ammonia synthesis catalyst) of Example 3 (reaction conditions: 400°C, 0.9 MPa). This is a graph showing the change over time in the catalytic activity (ammonia synthesis rate) of the catalyst composition (ammonia synthesis catalyst) of Example 6 (reaction conditions: 400°C, 0.9 MPa, N ２ / H ２ 1 is a graph showing the change over time in catalytic activity (ammonia synthesis rate) of the catalyst composition (ammonia synthesis catalyst) of Example 7 (reaction conditions: 400° C., 0.9 MPa, N ２ / H ２ = 1 / 3).

[0012] (Terminology)

[0013] In the present invention, "ammonia synthesis activity" means having catalytic activity for the ammonia synthesis reaction. Furthermore, "a catalyst having ammonia synthesis activity" and "ammonia synthesis catalyst" mean a catalyst having catalytic activity for the ammonia synthesis reaction.

[0014] In the present invention, the term "catalytically active metal" means a metal that has catalytic activity for the ammonia synthesis reaction.

[0015] In the present invention, the term "precursor of the catalytic substance" refers to a raw material or intermediate product for producing the catalytic substance. When the raw material or intermediate product contains two compounds, the precursor of the catalytic substance may be a mixture. For example, in the specific example of Example 1, "MgO+Ba(NO ３ ) ２ " is a precursor of the catalytic material Ba-MgO. Also, "a precursor of a catalytically active metal" means a raw material or intermediate product for producing a catalytically active metal. When the raw material or intermediate product contains two compounds, the precursor of the catalytically active metal may be a mixture. For example, in the specific example of Example 1, "Co ２ (CO) ８ " is a precursor of Co, which is a catalytically active metal. A "precursor of a catalytically active metal" is sometimes referred to as a catalytically active metal compound.

[0016] (Catalyst Composition) The catalyst composition of the present embodiment contains an additive represented by the following formula (1) and a catalyst material represented by the following formula (2): AH ２－ｘ (1) (In formula (1), A is a metal element including at least one selected from the group consisting of Zr and Mg, and x is a value in the range of 0≦x≦2.) M ｐ O ｑ C ｗ N ｓ H ｔ(2) (In formula (2), M represents one or more elements selected from the group consisting of typical elements and transition elements, with the proviso that M does not contain aluminum (Al) and calcium (Ca) at the same time, p represents a numerical value of 1 or more, q represents a numerical value of 0 or more, w represents a numerical value of 0 or more, s represents a numerical value of 0 or more, and t represents a numerical value of 0 or more, with the proviso that q, w, s, and t are not all 0 at the same time.) In formula (1), it is preferable that A represents at least one element selected from the group consisting of Zr and Mg.

[0017] The catalyst composition of this embodiment may or may not have ammonia synthesis activity.

[0018] The additive contained in the catalyst composition of this embodiment may or may not have ammonia synthesis activity.

[0019] [Additive] In the additive according to this embodiment, in the formula (1), x preferably represents a value of 0≦x<2, and more preferably 0≦x<1.5. In the additive according to this embodiment, in the formula (1), A is preferably Zr. The additive is preferably at least one selected from the group consisting of zirconium hydride, magnesium hydride, metallic zirconium, and metallic magnesium, and more preferably at least one selected from the group consisting of zirconium hydride, magnesium hydride, and metallic zirconium. The additive may be zirconium hydride alone, magnesium hydride alone, or metallic zirconium alone. Alternatively, it may be a combination of two or more selected from the group consisting of zirconium hydride, magnesium hydride, metallic zirconium, and metallic magnesium. Here, zirconium hydride refers to ZrH ２ , ZrH １．５ , ZrH １．０ etc.ZrH ２－ｘ (x is 0≦x<2). In the present invention, unless otherwise specified, ZrH ２ When describing zirconium hydride (ZrH ２－ｘ (x is 0≦x<2)

[0020] In the additive according to this embodiment, in the formula (1), A contains Mg and may further contain Ni or Al. For example, when A contains Mg and Ni, the molar ratio may be 5:1 to 3:1, or may be 2.5:1 to 2:1. When A contains Mg and Al, the molar ratio may be 3:1 to 2:1, or may be 2.5:1 to 1:1. A=Mg ２ For the additive according to the present embodiment, in the formula (1), when A contains Mg and further contains Ni or Al, it is preferable that x=2.

[0021] The additive according to this embodiment can be obtained from a commercial product. The form of the additive is not particularly limited, and powder, granules, etc. can be used from the viewpoint of uniform mixing with other raw materials in the subsequent method for producing a catalyst composition. As the additive according to this embodiment, for example, ZrH ２ (40 μm, Zr+Hf: 97.6%, H: 2.1%), MgH manufactured by Fujifilm Wako Co., Ltd. ２ , Zr (403296, 100 mesh) manufactured by Aldrich, and the like.

[0022] The amount of additive added according to this embodiment is the content of the additive relative to 100% by mass of the final catalyst composition. It is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 20% by mass or more. It is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 45.0% by mass or less.

[0023] [Catalyst Material (Support)] In the catalyst material (support) according to this embodiment, in the formula (2), M represents one or more elements selected from the group consisting of barium (Ba), cerium (Ce), magnesium (Mg), calcium (Ca), strontium (Sr), lanthanum (La), silicon (Si), and aluminum (Al), p is preferably a numerical value of 1 or greater, q is preferably a numerical value of 1 or greater, w is preferably a numerical value of 0 or greater, s is preferably a numerical value of 0 or greater, and t is preferably a numerical value of 0 or greater.

[0024] In the catalyst material (support) according to this embodiment, in the formula (2), M represents one or more elements selected from the group consisting of barium (Ba), cerium (Ce), magnesium (Mg), calcium (Ca), strontium (Sr), and lanthanum (La), p is a numerical value of 1 or more, q is a numerical value of 1 or more, w is 0, s is 0, and t is 0.

[0025] The catalyst material (support) according to this embodiment is preferably a basic metal oxide, and more preferably a crystalline basic metal oxide. Examples of basic metal oxides include BaO, SrO, MgO, CaO, and CeO. ２ , La ２ O ３ , Y ２ O ３ , BaAl ２ O ４ , MgAl ２ O ４ Or, a composite oxide thereof may be used.

[0026] The catalyst material (support) according to this embodiment is more preferably a catalyst material represented by the following formula (2-1).

[0027] M ｐ O ｑ (2-1)

[0028] In formula (2-1), M represents one or more elements selected from the group consisting of typical elements and transition elements, provided that M does not contain aluminum (Al) and calcium (Ca) at the same time. It is also preferred that p represents a value greater than 0, q represents a value greater than 0, w represents a value greater than 0, s represents a value greater than 0, and t represents a value greater than 0.

[0029] "Compound of Formula (2-1)" The compound of the above formula (2-1) may be a main group element oxide represented by the following general formula (2-1a): ｎ B ｍ O ｌ (2-1a)

[0030] In the general formula (2-1a), A is at least one selected from the group consisting of Ba and Sr, B is at least one selected from the group consisting of Al, Ga, In, Si, Ge, and Sn, n is an integer of 1 to 17, m is an integer of 1 to 17, and l is a number represented by an integer of 1 to 26. It is preferable that l is 4 or 5.

[0031] In this embodiment, the term "typical element" refers to an element of Groups 1, 2, and 12 to 18 of the periodic table. That is, it does not refer to a transition element (an element of Groups 3 to 11 of the periodic table) of Groups 3 to 11 of the periodic table. The "typical element oxide" or "typical element composite oxide" of the present invention preferably contains 90% by mass or more of an oxide or composite oxide composed of a typical element (an element of Groups 1, 2, and 12 to 18 of the periodic table) excluding oxygen and oxygen. It preferably contains 95% by mass or more, 99% by mass or more, or substantially 100% by mass. It is even more preferable to contain substantially 100% by mass. "Containing substantially 100% by mass" means, for example, that the transition element content is less than 1% by mass or less than 0.5% by mass. The metal-supported support of the present invention preferably contains 50% by mass or more of the typical element oxide or "typical element composite oxide" of the present invention. It is more preferable to contain 70% by mass or more. It is more preferable that the content is 90% by mass or more. It is particularly preferable that the content is substantially 100% by mass or more. "Substantially 100% by mass" means that the content of transition element oxides, calculated as transition elements, is less than 1% by mass or less than 0.5% by mass, for example.

[0032] Specific examples of the typical element oxide of this embodiment include BaAl ２ O ４ , Ba ３ Al ２ O ６ , Ba ４ Al ２ O ７ , Ba １７ Al ３ O ７ , BaAl ４ O ７ , BaAl １２ O １９ , BaGa ２ O４ 、BaGa ４ O ７ 、Ba ４ Ga ２ O ７ 、Ba ３ Ga ２ O ６ 、BaInO ２．５ 、Ba ３ In ２ O ６ 、Ba ８ In ６ O １７ 、Ba ２ In ２ O ５ 、Ba ４ In ２ O ７ 、Ba ４ In ６ O １３ 、SrAl ２ O ４ 、SrAl １２ O １９ 、SrAl ４ O ７ 、Sr ４ Al １４ O ２５ 、Sr ９ Al ６ O １８ 、Sr ３ Al ２ O ６ 、Sr １０ Al ６ O １９ 、Sr ２ Al ６ O １１ 、Sr ７ Al １２ O ２５ 、SrGa ２ O ４ 、Sr ３ Ga ４ O ９ 、SrGa １２ O １９ 、Sr １０ Ga ６ O １９ 、Sr ３ Ga ２ O ６ 、Sr ４ Ga ２ O ７ 、Sr ２Ga ２ O ５ 、Sr ５ Ga ６ O １４ 、SrGa ４ O ７ 、Ba ３ SiO ５ 、Ba ２ SiO ４ 、Ba ２ Si ４ O １０ 、Ba ４ Si ６ O １６ 、BaSi ４ O ９ 、Ba ５ Si ８ O ２１ 、Ba ６ Si １０ O ２６ 、BaSiO ３ 、BaSi ２ O ５ 、Ba ３ GeO、BaGe ４ O ９ 、BaGe ２ O ５ 、Ba １０ Ge ７ O ３ 、BaGeO ３ 、Ba ３ Ge ３ O ９ 、Sr ３ SiO ５ 、Sr ３ Si ３ O ９ 、Sr ４ Si ４ O １２ 、Sr ２ SiO ４ 、SrSiO ３ 、SrSi ２ O ５ 、Sr ３ SiO、Sr ３ GeO、Sr ２ GeO ４ 、SrGeO ３ 、SrGe ４ O ９ 、SrGe ２ O ５Among them, BaAl is the most popular from the viewpoints of availability, ease of preparation, and versatility. ２ O ４ , Ba ２ SiO ４ , Ba ３ SiO ５ is preferred, and BaAl ２ O ４ is more preferred.

[0033] [Method for producing a main group element oxide] BaAl ２ O ４ Synthesis examples of Ba ２ SiO ４ The synthesis of BaAl is explained below. ２ O ４ 0.148 g of barium carbonate (Wako Pure Chemical Industries, 99.9%) and 0.117 g of aluminum hydroxide (Kojundo Chemical, 99.99%) were mixed in a molar ratio of 1:2, and the resulting mixture was placed in an alumina crucible and heated to 1000°C for 3 hours and maintained at that temperature for 10 hours to obtain BaAl ２ O ４ get.

[0034] <Ba ２ SiO ４ Synthesis of Ba(CH ３ COO) ２ (Kanto Chemical, 9.0%) and TEOS (tetraethylene orthosilicate) are reacted by complex polymerization using ethylene glycol (Kanto Chemical / Wako Pure Chemical, 99.0%) in which citric acid (Kanto Chemical, 99.0%) has been dissolved in advance as a solvent. ２ SiO ４ A stoichiometric amount of Ba (raw material) was prepared, and this was placed in a beaker with a stirrer using ethylene glycol, in which citric acid had been dissolved in advance, as a solvent, and stirred overnight at 120°C. The mixture was then heated to 180°C and held for 6 hours to obtain a brown gel-like substance. The beaker was then transferred to a mantle heater and held at 450°C for 2 hours to obtain a black powder. The black powder obtained was placed in an alumina crucible, heated to 800°C for 40 minutes in an electric furnace, and held at 800°C for 4 hours to obtain the target white powder Ba. ２ SiO ４ get.

[0035] <Oxide of a Group 13 Main Group Element> The oxide of a main group element according to this embodiment may be a composite oxide of a main group element represented by the following general formula (2-1b): AB ２ O ｌ (2-1b) (In the general formula (2-1b), B is at least one selected from the group consisting of Al, Ga, and In, l represents a number satisfying the formula 3.5≦l≦4.5, and A has the same meaning as A in the general formula (1)).

[0036] The compound represented by the general formula (2-1b) is a compound in which, in the compound represented by the general formula (2-1a), n is 1, m is 2, l is a number satisfying 3.5≦l≦4.5, and B is at least one selected from the group consisting of Al, Ga, and In.

[0037] In the general formula (2), l preferably represents a number that satisfies 3.8≦l≦4.2, more preferably a number that satisfies 3.9≦l≦4.1, and more preferably 4. For example, BaAl ２ O ４ can be used.

[0038] <Typical element oxide containing a typical element of Group 14> The typical element oxide of this embodiment is a typical element oxide represented by the following general formula (2-1c): ２ BO ｌ (2-1c) (In the general formula (3), B is at least one selected from the group consisting of Si, Ge, and Sn, l represents a number satisfying the formula 3.5≦l≦4.5, and A has the same meaning as A in the general formula (2-1a)).

[0039] The compound represented by the general formula (2-1c) is a compound in which, in the compound represented by the general formula (2-1a), n is 2, m is 1, l is a number satisfying 3.5≦l≦4.5, and B is at least one selected from the group consisting of Si, Ge, and Sn.

[0040] In the general formula (2-1c), l preferably represents a number expressed by 3.8≦l≦4.2, more preferably a number expressed by 3.9≦l≦4.1, and even more preferably l is 4.

[0041] The compound of the above formula (2-1) may be a composite oxide represented by the following general formula (2-1d): ｎ X ｙ M ｍ O ｘ (2-1d) (In the general formula (2-1d), A is a rare earth element characterized in that at least a part or all of it is in a trivalent state, X is any of Group 2 elements, Group 4 elements, and rare earth elements in the periodic table, and is an element different from A, M is any of Group 2 elements, Group 4 elements, and rare earth elements in the periodic table, and is an element different from A and X, n is 0<n<1, y is 1-n, m is 0≦m≦0.5, and x is the number of oxygen atoms necessary for the composite oxide to maintain electrical neutrality.

[0042] Examples of such element A include lanthanides, preferably Ce, Pr, Tb, and La. Ce and La are more preferred, and Ce is most preferred. The element X constituting the composite oxide of general formula (2-1d) is selected from, for example, Group 2 elements of the periodic table such as Mg, Ca, Sr, and Ba; Group 4 elements such as Ti, Zr, and Hf; or rare earth elements such as Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; and X and M are not the same as the other element A constituting the composite oxide. When element M is a Group 2 element of the periodic table, it is preferably selected from Ca, Sr, and Ba. Furthermore, when element M is a rare earth, it is preferably a lanthanide.

[0043] The element M constituting the composite oxide of the general formula (2-1d) is selected from, for example, Group 1 elements of the periodic table such as Na, K, Rb, Cs, Fr, etc., Group 2 elements of the periodic table such as Mg, Ca, Sr, Ba, etc., Group 4 elements such as Ti, Zr, or Hf, or rare earth elements such as Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu, and is not the same as the other element A constituting the composite oxide, and X and M are not the same. When the element X is a Group 2 element of the periodic table, it is preferably selected from Ca, Sr, or Ba. When the element X is a rare earth, it is preferably a lanthanoid. In particular, from the viewpoint of ammonia synthesis activity, the element M is preferably Ba. The raw material of Ba can be, for example, BaO, Ba(NO ３ ) ２ , or BaCl ２ ・2H ２ O, Ba(OH) ２ , Ba(OH) ２ ・8H ２ O, Ba(CH ３ COO) ２ , BaCO ３ In consideration of industrial applicability, Ba(NO ３ ) ２ and Ba(OH) ２ ・8H ２ O can be given.

[0044] Preferably, X and M are selected from Zr and La. The composite oxide of the present invention may contain two types of Group 4 elements or rare earth elements as X and M, or may contain only one type of Group 4 element or rare earth element as X (m=0 in general formula (2-1d)).

[0045] When the composite oxide of the present invention is represented by general formula (2-1d), the ranges of n, y, m, and x are as follows. In general formula (2-1d), which represents the proportion of element A in the composite oxide, n is 0<n<1, preferably 0.05<n<0.95, more preferably 0.1<n<0.9, and particularly preferably 0.35≦n≦0.5. In general formula (2-1d), which represents the proportion of element X in the composite oxide, y is 0<y<1, preferably 0.05<y<0.95, more preferably 0.1<y<0.9, and particularly preferably 0.35≦y≦0.5.

[0046] In general formula (2-1d), m represents the proportion of element M in the composite oxide, and is 0≦m<1. In general formula (2), m is 0≦m≦0.5. In both formulas (1) and (2), m is preferably 0<m<0.5, more preferably 0.05≦m≦0.45, and particularly preferably 0.1≦m≦0.3. When m=0, the composite oxide is composed only of A, X, and O.

[0047] For example, La ０．５ Ce ０．５ O １．７５ In the case of a binary support containing two metal elements such as those shown in (1), when these elements are a composite of a lanthanide element, a uniform solid solution is often formed. Ru particles are in direct contact with the surface. When Ce is reduced, since both La and Ce are strongly basic elements in the oxide state, it is presumed that there are many active sites with Ru, resulting in high ammonia synthesis activity.

[0048] On the other hand, for example, Ba ０．１ La ０．４５ Ce ０．４５ O ｘIn the case of a ternary support containing three metal elements, as shown in Figure 1, Ba has a larger atomic radius than La and Ce. In this case, when the calcination temperature of the raw material mixture is high, for example, when the calcination temperature exceeds 1000°C, all elements are uniformly dissolved, resulting in a perovskite-type crystal structure. On the other hand, when the calcination temperature of the raw material mixture is low, Ba is a large element and does not easily dissolve in solid solution with other elements. Therefore, a structure is formed in which Ba is unevenly mixed in the solid solution of La and Ce, and a portion of Ba is exposed on the surface of the solid solution of La and Ce. Since Ba is a strongly basic element with a higher partial negative charge of oxygen than La and Ce, a support on which Ba is unevenly exposed increases the contact area between Ba and Ru, increasing the number of active sites. This is presumably why the ammonia synthesis activity is high.

[0049] Specific examples of the composite oxide of this embodiment include the following: Ce ０．５ La ０．５ O ｘ Pr ０．５ La ０．５ O ｘ Ba ０．３ Pr ０．３５ Ce ０．３５ O ｘ Ba ０．１ La ０．４５ Ce ０．４５ O ｘ

[0050] <Method for Producing Composite Oxide> The composite oxide of this embodiment can be produced by the following method. The method includes: (a) a mixing step of mixing an A precursor containing element A, an X precursor containing element X, and an M precursor containing element M to obtain a mixture; and (b) a firing step of firing this mixture. The above specific example of the composite oxide of this embodiment can be synthesized by the same method as disclosed in the examples of Patent Document 7.

[0051] The catalyst material (support) according to this embodiment may be Ba—MgO, Sr—MgO, BaAl ２ O ４ , CeO ２ , Ba—CeO ２ , Ba-MgAl ２ O ４Among them, Ba—MgO, BaAl ２ O ４ , CeO ２ , Ba—CeO ２ , Ba-MgAl ２ O ４ It is preferable that:

[0052] [Catalytically Active Metal] The catalyst composition of this embodiment preferably further contains a catalytically active metal. It is more preferable that the catalytically active metal is supported on the catalytic substance contained in the catalyst composition. The catalytically active metal supported on the catalytic substance serving as the support is called a metal support. That is, the catalyst composition of this embodiment preferably contains the additive and the metal support. It is preferable that the catalytically active metal is a transition metal. The transition metal used in this embodiment is not particularly limited, but is usually a transition metal of Group 6, 7, 8, 9, or 10 of the periodic table, preferably a transition metal of Group 6, 8, or 9, and more preferably a metal of Group 8 or 9.

[0053] The catalytically active metal according to this embodiment is preferably at least one selected from the group consisting of ruthenium (Ru), cobalt (Co), iron (Fe), nickel (Ni), molybdenum (Mo), rhodium (Rh), rhenium (Re), chromium (Cr), and manganese (Mn). The catalytically active metal according to this embodiment is more preferably at least one selected from the group consisting of cobalt (Co) and iron (Fe). The catalytically active metal according to this embodiment is even more preferably cobalt (Co).

[0054] The above elements may be used alone or in combination of two or more. Intermetallic compounds of these elements, such as Co ３ Mo ３ N, Fe ３ Mo ３ N, Ni ２ Mo ３ N, Mo ２N, etc. can also be used. Preferably, each element is used alone or in combination of two or more kinds, and more preferably, it is advantageous in terms of cost to use each element alone. When the catalyst composition of this embodiment contains the catalytically active metal, in the catalyst composition, each of the above elements of the catalytically active metal may be present in the form of a simple metal, a metal alloy, an intermetallic compound, a metal oxide, a metal nitride, or the like. For example, when the catalytically active metal is cobalt (Co), in the catalyst composition, cobalt (Co) may be cobalt metal, or cobalt oxide (CoO ｘ ) may also be present.

[0055] In the metal-supported material using the catalytic substance as a support, the amount of the transition metal supported is not particularly limited, but is usually 0.01 parts by mass (0.01% by mass) or more, preferably 0.5 parts by mass (0.5% by mass) or more, more preferably 1 part by mass (1% by mass) or more, and even more preferably 2 parts by mass (2% by mass) or more, relative to 100 parts by mass of the support, and is usually 50 parts by mass (50% by mass) or less, preferably 30 parts by mass (30% by mass) or less, more preferably 20 parts by mass (20% by mass) or less, and even more preferably 10 parts by mass (10% by mass) or less. If the amount is equal to or greater than the lower limit, the effects of the present invention can be obtained, and if the amount is equal to or less than the upper limit, the effects of the present invention can be obtained in which the amount supported is commensurate with the cost.

[0056] The method for supporting the transition metal (M) on the catalytic material (support) is not particularly limited, but a supported material (metal-supported material) in which the transition metal (M) is fixed to the catalytic material (support) can be obtained, for example, by the following method. The above method includes, for example, a step of dispersing both the catalytic material (support) and a precursor of the metal to be supported in an aqueous solution and stirring the mixture; a step of drying the mixture obtained after stirring at 140°C for about 2 hours; and a step of heating the dried material obtained at 400°C for 4 hours in a nitrogen atmosphere to thermally decompose the metal compound.

[0057] For example, examples of transition metal compounds in which the transition metal (M) is Ru, Co, or Fe include nitrates, formates, hydroxides, carbonates, acetates, and carbonyl complexes. Specifically, for example, Ru transition metal compounds include Ru ３ (CO)１２ or Ru(NO)(NO ３ ) ３ The Co transition metal compound can be Co(OH). ２ , Co(NO ３ ) ２ ・6H ２ O or CoCO ３ , Co(CH ３ COO) ２ ・4H ２ O can be used. The Fe transition metal compound is Fe(CH ３ OO) ２ , Fe(OH) ２ , Fe(NO ３ ) ３ ・9 (H ２ These compounds can be used to prepare metal supports such as Ru-supported supports (abbreviated as Ru / support), Co-supported supports (abbreviated as Co / support), etc. 、 An Fe-supported material (abbreviated as Fe / support) can be synthesized.

[0058] <Specific Examples of Catalyst Compositions> Specific examples of the catalyst composition of the present embodiment include catalyst compositions using the following additives, catalytic substances, and catalytically active metals. (I) Additive: ZrH ２ , MgH ２ , Zr, and Mg. Catalytic material: Ba—MgO, Sr—MgO, BaAl ２ O ４ , CeO ２ , and Ba—CeO ２ , Ba-MgAl ２ O ４ Catalytically active metal: one selected from the group consisting of Ru, Co, and Fe

[0059] (II) Additive: ZrH ２ , MgH ２ and Zr. Catalytic material: Ba—MgO, Sr—MgO, BaAl ２ O ４ , CeO ２ , and Ba—CeO ２ , Ba-MgAl ２ O ４Catalytically active metal: one selected from the group consisting of Ru, Co, and Fe

[0060] (III) Additive: ZrH ２ , MgH ２ and Zr. Catalytic material: Ba—MgO, Sr—MgO, BaAl ２ O ４ , CeO ２ , and Ba—CeO ２ , Ba-MgAl ２ O ４ Catalytically active metal: one selected from the group consisting of Co and Fe

[0061] (IV) Additive: ZrH ２ , MgH ２ and Zr. Catalytic material: Ba—MgO, Sr—MgO, BaAl ２ O ４ , CeO ２ , and Ba—CeO ２ , Ba-MgAl ２ O ４ Catalytically active metal: Co

[0062] (Method for Producing Catalyst Composition) A method for producing a catalyst composition according to one embodiment of the present invention is a method for producing the catalyst composition. The method for producing a catalyst composition according to this embodiment includes a step of mixing the additive with the catalytic substance or a precursor thereof. When the catalyst composition includes the catalytically active metal, the method for producing a catalyst composition according to this embodiment includes a first step of mixing the catalytic substance or a precursor thereof with the catalytically active metal and its precursor; a second step of reacting the first mixture obtained in the first step to support the catalytically active metal on the catalytic substance and obtain a metal-supported material; and a third step of mixing the additive with the metal-supported material. In the second step, the first mixture obtained in the first step is preferably reacted at a temperature of 600°C or less to support the catalytically active metal on the catalytic substance. The temperature may be 550°C or less, 500°C or less, or 450°C or less. Alternatively, the temperature may be 300°C or more. The reaction may be carried out in the atmosphere.

[0063] Preferred aspects and specific examples of the additives, catalytic substances, and catalytically active metals used in the production method of this embodiment can be derived from the preferred aspects and specific examples described above for the catalyst composition.

[0064] (Ammonia synthesis catalyst) An ammonia synthesis catalyst according to one embodiment of the present invention comprises the above-described catalyst composition, and is preferably the above-described catalyst composition. The ammonia synthesis catalyst according to this embodiment preferably comprises the above-described catalytically active metal.

[0065] (Pretreatment of catalyst) When ammonia is produced using the ammonia synthesis catalyst of this embodiment, it is preferable to pretreat the catalyst before the ammonia synthesis reaction. The pretreatment may be, for example, a heat treatment method at less than 600°C in a reducing atmosphere such as a hydrogen gas atmosphere or a hydrogen and nitrogen mixed gas atmosphere. The treatment temperature is preferably 550°C or less, more preferably 500°C or less, even more preferably 450°C or less, and most preferably 400°C or less. It may also be 300°C or more. The hydrogen gas atmosphere may contain an inert gas other than nitrogen. The hydrogen and nitrogen mixed gas atmosphere may also contain ammonia gas. The hydrogen and nitrogen mixed gas atmosphere may be, for example, a hydrogen to nitrogen mixed gas atmosphere having a volume ratio of hydrogen to nitrogen (H ２ / N ２ ) is preferably 1 to 5, more preferably 2 to 4, and even more preferably 2.3 to 3.5. ２ , H ２ Under a gas atmosphere (H ２ / N ２ The catalyst was pretreated under the conditions of (V / V) 0.05 (V / V) / 450°C for 20 hours. The catalytic activity (ammonia synthesis rate) of the ammonia synthesis catalyst of the examples was evaluated by measuring the catalytic activity after the above pretreatment by changing the reaction temperature, reaction pressure, raw material gas ratio, etc. to a predetermined value.

[0066] The catalyst composition and ammonia synthesis catalyst of the present invention include both the form before the pretreatment and the form after the pretreatment. Furthermore, the ammonia synthesis catalyst of the present invention also includes the form after it has been used in an ammonia synthesis reaction.

[0067] (Method for Producing Ammonia) The method for producing ammonia of this embodiment is a method for producing ammonia, comprising a step of reacting nitrogen and hydrogen in the presence of the catalyst composition (ammonia synthesis catalyst) of this embodiment. The specific production method is not particularly limited as long as it is a method for synthesizing ammonia by bringing hydrogen and nitrogen into contact on the catalyst, and ammonia can be produced according to any known production method.

[0068] In the ammonia production method of this embodiment, ammonia is usually produced by heating the catalyst when hydrogen and nitrogen are brought into contact on the catalyst. The reaction temperature in the production method of this embodiment is not particularly limited, but is usually 200°C or higher, preferably 250°C or higher, more preferably 300°C or higher, and usually 600°C or lower, preferably 500°C or lower, more preferably 450°C or lower. Since ammonia synthesis is an exothermic reaction, a lower temperature range is advantageous for ammonia production in terms of chemical equilibrium, but in order to obtain a sufficient ammonia production rate, it is preferable to carry out the reaction within the above temperature range. In the production method of this embodiment, the molar ratio of nitrogen and hydrogen brought into contact with the catalyst is not particularly limited, but is usually the ratio of hydrogen to nitrogen (H ２ / N ２ The mixing ratio (volume / volume) is usually 0.4 or more, preferably 0.5 or more, more preferably 1 or more, and usually 10 or less, preferably 5 or less.

[0069] The reaction pressure in the production method of this embodiment is not particularly limited, but is usually 0.01 MPa or more, preferably 0.1 MPa or more, and usually 20 MPa or less, preferably 15 MPa or less, more preferably 10 MPa or less, as the pressure of the mixed gas containing nitrogen and hydrogen. In consideration of practical use, it is preferable to carry out the reaction under pressurized conditions of atmospheric pressure or higher.

[0070] In the production method of this embodiment, before nitrogen and hydrogen are brought into contact with the catalyst, it is preferable to remove moisture and oxides adhering to the catalyst using a method that uses a dehydrating agent, a cryogenic separation method, hydrogen gas, or the like. Examples of removal methods include reduction treatment. In the production method of this embodiment, in order to obtain a better ammonia yield, it is preferable that the moisture content of the nitrogen and hydrogen used in the production method of this embodiment is low. Although not particularly limited, it is generally preferable that the total moisture content in the mixed gas of nitrogen and hydrogen is 100 ppm or less, preferably 50 ppm or less.

[0071] In the production method of this embodiment, the type of reaction vessel is not particularly limited, and a reaction vessel typically used for ammonia synthesis reactions can be used. Specific reaction types that can be used include, for example, a batch reaction type, a closed circulation reaction type, and a flow reaction type. Among these, a flow reaction type is preferred from a practical standpoint. Furthermore, any of the following methods can be used: a single type of reactor packed with a catalyst, a method in which multiple reactors are connected, or a reactor having multiple reaction layers within the same reactor. Since the reaction of synthesizing ammonia from hydrogen and nitrogen is an exothermic reaction accompanied by volume contraction, industrially, it is preferable to remove the heat of reaction to increase the ammonia yield. A known reaction apparatus equipped with a commonly used heat removal means may be used. Specifically, for example, a method in which multiple reactors packed with a catalyst are connected in series and an intercooler is installed at the outlet of each reactor to remove heat may be used.

[0072] In the ammonia production method of the present embodiment, the ammonia synthesis catalyst obtained by the production method of the present embodiment can be used alone or in combination with other known catalysts that can be normally used for ammonia synthesis.

[0073] The preferred aspects and specific examples of the catalyst composition according to the production method of this embodiment can be derived from the preferred aspects and specific examples of the catalyst composition described above.

[0074] The present invention will be described in more detail below based on examples. ３ The amount of produced NH ３ The ammonia synthesis activity was evaluated by dissolving the compound in an aqueous sulfuric acid solution and quantifying the ammonia production rate by ion chromatography.

[0075] (Ion chromatogram analysis) Ammonia gas discharged from the reaction vessel was dissolved in a 5 mM aqueous sulfuric acid solution, and the captured ammonium ions (NH ４ ＋ ) was analyzed by ion chromatography under the following analytical conditions:

[0076] [Measurement conditions] Apparatus: Prominence manufactured by Shimadzu Corporation Detector: Electrical conductivity detector CDD-10Avp (manufactured by Shimadzu Corporation) Column: Ion chromatogram column IC-C4 (manufactured by Shimadzu Corporation) Eluent: 3.0 mM oxalic acid + 2.0 mM 18-crown-6-ether aqueous solution Flow rate: 1.0 mL / min Column temperature: 40°C (XRD) Apparatus and measurement conditions Apparatus: Bruker D2 PHASER X-ray source: CuKα Measurement angle range: 10 to 80°

[0077] (Example 1) "Preparation of catalyst composition (catalyst for ammonia synthesis)" [ZrH ２ Synthesis of added Co / Ba—MgO powder]

[0078] Ba(NO ３ ) ２ 4.00 mL of DMSO (Fujifilm Wako Co., Ltd.) was added to 0.987 g of Ba-doped MgO (Kanto Chemical, special grade, 99%), and the mixture was kneaded together with 10.0 g of MgO (Ube Materials, 500A, average particle size: 50 nm, purity: 99.98%) in a mortar for about 15 minutes. The mixture was dried at 100°C for about 15 minutes. The resulting mixture was fired in an electric furnace at 700°C for 6 hours. 3.00 g of the obtained Ba-doped MgO powder and Co(NO ３ ) ２ ・6H ２ 3.704 g of Ba-MgO (Fuji Film Wako Co., Ltd., 99.5%) and 1.2 mL of ethylene glycol solution were kneaded in a pot for about 15 minutes (corresponding to 20 mass% of supported metal Co relative to 100 mass% of the total of metal Co and Ba-MgO). The resulting mixture was fired in an electric furnace at 500°C for 6 hours. The resulting powder (CoO ｘ / Ba-MgO) and 3.00 g of ZrH ２ 0.933g (CoO ｘ / Ba-MgO as an additive amount of 25 mass%) is dry mixed to obtain ZrH ２ Added CoO ｘ A mixture of ZrH ２ Added CoO ｘ / Ba-MgO" is simply "ZrH ２ Additive Co / Ba-MgO" or "ZrH２ -Co / Ba-MgO".

[0079] [ZrH ２ Ammonia synthesis using added Co / Ba—MgO] <Ammonia synthesis reaction> ２ The catalyst was added Co / Ba-MgO and mixed gas of nitrogen and hydrogen (N ２ / H ２ The ammonia synthesis reaction was carried out by contacting the ZrH ２ 0.1 g of the added Co / Ba-MgO was packed into an SUS reaction tube, and the reaction was carried out using a fixed-bed flow reactor incorporating the reaction tube. The moisture concentrations of the raw material nitrogen gas and hydrogen gas were each below the detection limit. The flow rates of the raw material gases during this reaction were 15 mL / min for nitrogen gas and 45 mL / min for hydrogen gas (total 60 mL / min). The reaction pressure during this reaction was 0.9 MPa, the reaction temperature was 400°C, and the reaction time was 30 hours. As a pretreatment reaction before the reaction, the reaction was carried out at 450°C for 20 hours under the same conditions as the ammonia synthesis reaction described above. The reaction conditions were then set and the catalytic activity was evaluated.

[0080] <Ammonia Production Rate> The gas coming out of the fixed-bed flow reactor was bubbled into a 0.005 M aqueous sulfuric acid solution, thereby dissolving the ammonia in the gas into the aqueous solution. The ammonium ions produced in the aqueous solution were quantified by the above-mentioned method using ion chromatography. The production rate of ammonia produced by the ammonia synthesis reaction was measured over time by ion chromatography, and as a result, ZrH ２ The Co / Ba-MgO catalyst showed high catalytic activity. ２ The ammonia production rate of the loaded Co / Ba-MgO catalyst was 32.1 mmol / g·hr. The results are shown in FIG.

[0081] <Stability of ammonia synthesis reaction> The ammonia synthesis rate was measured at 400°C and 0.9 MPa in the same manner as above, except that the reaction time was changed. The results are shown in Figure 2. ２The added Co / Ba-MgO catalyst exhibited stable catalytic activity with almost no decrease in the ammonia production rate even after continuous reaction for 200 hours or more.

[0082] <Recycling of Ammonia Synthesis Catalyst> After the ammonia synthesis reaction at 400°C and 0.9 MPa was carried out for 100 hours, the ammonia synthesis catalyst was removed from the reaction tube and exposed to the atmosphere for 3 hours. The ammonia synthesis reaction was then carried out again without pretreatment. The reaction time was varied, and the ammonia synthesis rate at 400°C and 0.9 MPa was measured in the same manner as above. The results are shown in Figure 3. The recycled catalyst showed almost no decrease in ammonia production rate even after continuous reaction for over 100 hours, demonstrating the recyclability of the catalyst. On the other hand, the Ti-added Co / Ba-MgO powder (Comparative Example 5) recovered only about half of its initial activity.

[0083] <Temperature Dependence of Ammonia Production Rate> The ammonia synthesis rate at 0.9 MPa was measured in the same manner as above, except that the reaction temperature was changed from 200°C to 400°C. The results are shown in Figures 4 and 5. ２ When using the added Co / Ba-MgO catalyst, 45.5 kJmol －１ showed a low activation energy of .

[0084] <Changes in additives before and after ammonia synthesis reaction> After the ammonia synthesis reaction was carried out at 400°C and 0.9 MPa for 30 hours, XRD analysis of the ammonia synthesis catalyst was carried out from the reaction tube. ２ The results are shown in FIG. 6 together with the XRD analysis data of the doped Co / Ba-MgO catalyst.

[0085] Example 2 [Synthesis of Zr-Added Co / Ba—MgO Powder] A Zr-added Co / Ba—MgO powder was obtained in the same manner as in Example 1, except that 0.933 g of Zr (addition amount: 25 mass % relative to Co / Ba—MgO (3 g)) was used as an additive.

[0086] [Ammonia synthesis using Zr-added Co / Ba—MgO] <Ammonia production rate> The ammonia production rate after 30 hours of reaction was measured in the same manner as in Example 1, except that Zr-added Co / Ba—MgO powder was used as the catalyst. It was 30.8 mmol / g hr. The results are shown in FIG. 1 and Table 1.

[0087] <Stability of Ammonia Synthesis Reaction> Except for using Zr-added Co / Ba—MgO powder as the catalyst, the stability of the ammonia synthesis reaction was evaluated in the same manner as in Example 1. The results are shown in FIG.

[0088] <Temperature Dependence of Ammonia Production Rate> The temperature dependence of the ammonia production rate was measured in the same manner as in Example 1, except that Zr-added Co / Ba—MgO powder was used as the catalyst. When a Zr-added Co / Ba—MgO catalyst was used, the temperature dependence of the ammonia production rate was 45.8 kJmol －１ The results are shown in Figures 4 and 5.

[0089] <Changes in additives before and after ammonia synthesis reaction> Except for using Zr-added Co / Ba—MgO powder as the catalyst, changes in additives before and after the ammonia synthesis reaction were evaluated in the same manner as in Example 1. XRD analysis data before and after the reaction are shown in FIG.

[0090] (Example 3) [MgH ２ Synthesis of Additive Co / Ba-MgO Powder] As an additive, MgH ２ The same method as in Example 1 was used except that 0.933 g of MgH (25 mass % as an additive amount relative to Co / Ba-MgO (3 g)) was used. ２ A doped Co / Ba-MgO powder was obtained.

[0091] [MgH ２ Ammonia synthesis using Co / Ba-MgO catalyst] <Ammonia production rate> ２ The ammonia production rate after 30 hours of reaction was measured in the same manner as in Example 1, except that additive Co / Ba-MgO powder was used. It was 29.4 mmol / g·hr. The results are shown in FIG. 1.

[0092] <Changes in additives before and after ammonia synthesis reaction> MgH２ Except for using additive Co / Ba—MgO, the change in additive before and after the ammonia synthesis reaction was evaluated in the same manner as in Example 1. XRD analysis data before and after the reaction are shown in FIG.

[0093] Example 4 [ZrH ２ Synthesis of Co(NO)-doped Fe / Ba-MgO powder ３ ) ２ ・6 (H ２ O) instead of Fe(NO ３ ) ３ ・9 (H ２ The ZrH of this example was prepared in the same manner as in Example 1, except that 5.246 g of ZrH (equivalent to 20 mass % of supported metal Fe relative to Ba-MgO) was used. ２ A doped Fe / Ba-MgO powder was obtained.

[0094] [ZrH ２ Ammonia synthesis using added Fe / Ba—MgO] <Ammonia production rate> ZrH ２ The ammonia production rate after 30 hours of reaction was measured in the same manner as in Example 1, except that additive Fe / Ba—MgO powder was used. It was 15.6 mmol / g·hr. The results are shown in FIG. 4 and Table 1.

[0095] Example 5 [ZrH ２ Added Co / Ba-MgAl ２ O ４ Powder synthesis] BaCO ３ (High Purity Chemical Research Institute, 99.95%) 2.25g, Al(OH) ３ (Kanto Chemical) 4.68g, Mg(OH) ２ 1.40 g of Ba-doped MgAl (Fujifilm Wako) was added to 6 mL of ethanol (Kanto Chemical Co., Ltd., 99.5%) and kneaded in a mortar for about 15 minutes. The mixture was dried at 100°C for about 15 minutes. The resulting mixture was fired in an electric furnace at 1000°C for 20 hours. ２ O ４ (Hereafter, simply referred to as "Ba-MgAl ２ O ４ " 1.60 g of the powder was added to Co(NO ３ ) ２ ・6H ２1.98 g of 0 (Fujifilm Wako Co., Ltd., 99.5%) and 0.60 mL of water were mixed in a mortar for about 15 minutes. (Metal Co equivalent and Ba-MgAl ２ O ４ The resultant mixture was fired in an electric furnace at 500°C for 6 hours. The powder (CoO ｘ / Ba-MgAl ２ O ４ ) and 3.00 g of ZrH ２ 0.933g (CoO ｘ / Ba-MgAl ２ O ４ By dry mixing ZrH ２ Added CoO ｘ / Ba-MgAl ２ O ４ Hereafter, a mixture of ZrH ２ Added CoO ｘ / Ba-MgAl ２ O ４ " is simply "ZrH ２ Added Co / Ba-MgAl ２ O ４ " or "ZrH ２ -Co / Ba-MgAl ２ O ４ " he says.

[0096] [ZrH ２ Added Co / Ba-MgAl ２ O ４ Ammonia synthesis using ZrH ２ Added Co / Ba-MgAl ２ O ４ The ammonia production rate after 30 hours of reaction was measured in the same manner as in Example 1, except that powder was used. It was 25.5 mmol / g·hr. The results are shown in Table 1.

[0097] (Example 6) [Mg ２ Synthesis of Ni-added Co / Ba-MgO powder] Mg ２ The same method as in Example 1 was used except that 1.0 g of Ni (Kojundo Chemical Laboratory) (25% by mass added to 3 g of Co / Ba-MgO) was used.２ Ni-added Co / Ba-MgO powder was obtained.

[0098] [Mg ２ Ammonia synthesis using Ni-added Co / Ba-MgO] <Ammonia production rate> ２ The ammonia production rate after 30 hours of reaction was measured in the same manner as in Example 1, except that Ni-added Co / Ba-MgO powder was used. It was 20.8 mmol / g·hr. The results are shown in FIG. 1 and Table 2.

[0099] <Stability of ammonia synthesis reaction> Mg ２ Except for using Ni-added Co / Ba—MgO powder, the stability of the ammonia synthesis reaction was evaluated in the same manner as in Example 1. The results are shown in FIG.

[0100] Example 7 Synthesis of MgAl-added Co / Ba—MgO powder The MgAl-added Co / Ba—MgO powder was obtained in the same manner as in Example 1, except that 1.0 g of MgAl (Kanto Metals) (addition amount: 25% by mass relative to Co / Ba—MgO (3 g)) was used as an additive.

[0101] [Ammonia synthesis using MgAl-added Co / Ba—MgO] <Ammonia production rate> The ammonia production rate after 30 hours of reaction was measured in the same manner as in Example 1, except that MgAl-added Co / Ba—MgO powder was used as the catalyst. It was 26.5 mmol / g hr. The results are shown in FIG. 1 and Table 2.

[0102] <Stability of Ammonia Synthesis Reaction> Except for using MgAl-added Co / Ba—MgO powder as the catalyst, the stability of the ammonia synthesis reaction was evaluated in the same manner as in Example 1. The results are shown in FIG.

[0103] Comparative Example 1 Synthesis of Additive-Free Co / Ba—MgO Powder Additive-free Co / Ba—MgO powder was obtained in the same manner as in Example 1, except that no additives were added.

[0104] [Ammonia synthesis using additive-free Co / Ba—MgO] <Ammonia production rate> The ammonia production rate after 30 hours of reaction was measured in the same manner as in Example 1, except that additive-free Co / Ba—MgO powder was used as the catalyst. It was 4.8 mmol / g hr. The results are shown in Figure 1.

[0105] Comparative Example 2 [Synthesis of Ni-added Co / Ba—MgO powder] Ni-added Co / Ba—MgO powder was obtained in the same manner as in Example 1, except that 0.933 g of Ni (addition amount: 25 mass % relative to Co / Ba—MgO (3 g)) was used as an additive.

[0106] [Ammonia synthesis using Ni-added Co / Ba—MgO] <Ammonia production rate> The ammonia production rate after 30 hours of reaction was measured in the same manner as in Example 1, except that Ni-added Co / Ba—MgO powder was used as the catalyst. It was 6.37 mmol / g hr. The results are shown in FIG. 1.

[0107] Comparative Example 3 Synthesis of TiO-Added Co / Ba—MgO Powder A TiO-added Co / Ba—MgO powder was obtained in the same manner as in Example 1, except that 0.933 g of TiO (addition amount: 25 mass % relative to Co / Ba—MgO (3 g)) was used as an additive.

[0108] [Ammonia synthesis using TiO-added Co / Ba—MgO] <Ammonia production rate> The ammonia production rate after 30 hours of reaction was measured in the same manner as in Example 1, except that TiO-added Co / Ba—MgO powder was used as the catalyst. It was 8.24 mmol / g hr. The results are shown in FIG. 1.

[0109] Comparative Example 4 [Synthesis of Al-Doped Co / Ba—MgO Powder] Al-doped Co / Ba—MgO powder was obtained in the same manner as in Example 1, except that 0.933 g of Al (addition amount: 25 mass % relative to Co / Ba—MgO (3 g)) was used as the additive.

[0110] [Ammonia synthesis using Al-doped Co / Ba—MgO] <Ammonia production rate> The ammonia production rate after 30 hours of reaction was measured in the same manner as in Example 1, except that Al-doped Co / Ba—MgO powder was used as the catalyst. It was 6.55 mmol / g hr. The results are shown in FIG. 1.

[0111] Comparative Example 5 [Synthesis of Ti-Added Co / Ba—MgO Powder] A Ti-added Co / Ba—MgO powder was obtained in the same manner as in Example 1, except that 0.933 g of Ti (25 mass % added relative to 3 g of Co / Ba—MgO) was used as an additive.

[0112] [Ammonia synthesis using Ti-added Co / Ba—MgO] <Ammonia production rate> The ammonia production rate after 30 hours of reaction was measured in the same manner as in Example 1, except that Ti-added Co / Ba—MgO powder was used as the catalyst. It was 9.88 mmol / g hr. The results are shown in FIG. 1.

[0113] <Temperature Dependence of Ammonia Production Rate> The temperature dependence of the ammonia production rate was measured in the same manner as in Example 1, except that Ti-added Co / Ba—MgO powder was used as the catalyst. When a Ti-added Co / Ba—MgO catalyst was used, the temperature dependence of the ammonia production rate was 60.8 kJmol －１ The results are shown in Figures 4 and 5.

[0114] (Comparative Example 6) [TiH ２ Synthesis of Additive Co / Ba—MgO Powder] As an additive, TiH ２ The same method as in Example 1 was used except that 0.933 g of TiH (25 mass % as an additive amount relative to Co / Ba—MgO (3 g)) was used. ２ A doped Co / Ba-MgO powder was obtained.

[0115] [TiH ２ Ammonia synthesis using Co / Ba-MgO added] <Ammonia production rate> ２ The ammonia production rate after 30 hours of reaction was measured in the same manner as in Example 1, except that additive Co / Ba-MgO powder was used. It was 9.5 mmol / g·hr. The results are shown in FIG. 1.

[0116] (Comparative Example 7) [LaH ３ Synthesis of Additive Co / Ba-MgO Powder] LaH ３ LaH was prepared in the same manner as in Example 1, except that 0.933 g (25 mass % added relative to Co / Ba—MgO (3 g)) was used. ３ A doped Co / Ba-MgO powder was obtained.

[0117] [LaH ３ Ammonia synthesis using Co / Ba-MgO added] <Ammonia production rate> LaH ３ The ammonia production rate after 30 hours of reaction was measured in the same manner as in Example 1, except that additive Co / Ba-MgO powder was used. It was 10 mmol / g·hr. The results are shown in FIG. 1.

[0118] (Comparative Example 8) [YH ３ Synthesis of Additive Co / Ba—MgO Powder] As an additive, YH ３ The same method as in Example 1 was used except that 0.933 g of TiH (25 mass % as an additive amount relative to Co / Ba—MgO (3 g)) was used. ２ A doped Co / Ba-MgO powder was obtained.

[0119] [Y.H. ３ Ammonia synthesis using Co / Ba-MgO added] <Ammonia production rate> ３ The ammonia production rate after 30 hours of reaction was measured in the same manner as in Example 1, except that additive Co / Ba—MgO powder was used. It was 16.7 mmol / g·hr. The results are shown in FIG. 1.

[0120]

[0121]

[0122] (Discussion) (1) From FIG. 1, for example, only elements Zr and Mg showed an effect. The reason for this is that, as shown by XRD, Zr and ZrH ２ After the reaction, ZrO ２This is thought to be because Zr abstracts lattice oxygen from BaO and promotes the formation of oxygen defects at low temperatures. (2) The element Mg as an additive exists on the surface of the catalyst in the form of a hydride and metal. The catalytic material (support) MgO exists in the catalyst in the form of a composite oxide with Ba. The element Mg as an additive and the element Mg in the support are thought to behave differently. MgH ２ As shown by XRD, the catalyst containing MgH ２ is visible, but after the reaction, oxygen is extracted from BaO and it is likely to become MgO. ２ In any case, the important thing is that oxygen is extracted from BaO to form BaO ｘ (3) Regarding stability and regeneration ability, ZrH ２ By extracting oxygen from BaO, BaO becomes highly electron donating. ｘ It is thought that high performance is achieved by forming seeds and donating electrons to the Co site, but after oxygen extraction, ZrO ２ etc. are BaO ｘ By covering the area around the seeds, BaO was able to be maintained even after exposure to the atmosphere. ｘ This is thought to prevent the reoxidation of the seeds.

Claims

1. A catalyst composition comprising an additive represented by the following formula (1) and a catalyst material represented by the following formula (2): AH ２－ｘ (1) (In formula (1), A is a metal element including at least one selected from the group consisting of Zr and Mg, and x is a value in the range of 0≦x≦2.) M ｐ O ｑ C ｗ N ｓ H ｔ (2) (In formula (2), M represents one or more elements selected from the group consisting of typical elements and transition elements, provided that M does not contain aluminum (Al) and calcium (Ca) at the same time, p represents a value of 1 or more, q represents a value of 0 or more, w represents a value of 0 or more, s represents a value of 0 or more, and t represents a value of 0 or more, provided that q, w, s, and t are not all 0 at the same time.) 2. The catalyst composition according to claim 1, wherein in formula (1), A represents at least one selected from the group consisting of Zr and Mg.

3. The catalyst composition according to claim 1, wherein in formula (2), M represents one or more elements selected from the group consisting of barium (Ba), cerium (Ce), magnesium (Mg), calcium (Ca), strontium (Sr), lanthanum (La), silicon (Si), and aluminum (Al), p is a numerical value of 1 or greater, q is a numerical value of 1 or greater, w is a numerical value of 0 or greater, s is a numerical value of 0 or greater, and t is a numerical value of 0 or greater.

4. The catalyst composition according to claim 1, wherein the catalyst material represented by formula (2) is a catalyst material represented by the following formula (2-1): M ｐ O ｑ (2-1) (In formula (2-1), M, p, and q have the same meanings as M, p, and q in formula (2) above.) 5. The catalytic material is Ba—MgO, Sr—MgO, BaAl ２ O ４ , CeO ２ , Ba—CeO ２ , Ba-MgAl ２ O ４ 2. The catalyst composition of claim 1, wherein the catalyst composition is one selected from the group consisting of:

6. The catalyst composition of claim 1 further comprising a catalytically active metal.

7. The catalyst composition according to claim 6, wherein the catalytically active metal is at least one selected from the group consisting of ruthenium (Ru), cobalt (Co), iron (Fe), nickel (Ni), molybdenum (Mo), rhodium (Rh), rhenium (Re), chromium (Cr), and manganese (Mn).

8. The catalyst composition of claim 7, wherein the catalytically active metal is cobalt (Co) or iron (Fe).

9. A method for producing a catalyst composition according to any one of claims 1 to 5, comprising the step of mixing the additive with the catalyst material or a precursor thereof.

10. A method for producing a catalyst composition according to any one of claims 6 to 8, comprising: a first step of mixing the catalyst substance or a precursor thereof with the catalytically active metal or a precursor thereof; a second step of reacting the first mixture obtained in the first step to cause the catalytically active metal to be supported on the catalyst substance, thereby obtaining a metal-supported material; and a third step of mixing the additive with the metal-supported material.

11. An ammonia synthesis catalyst using the catalyst composition according to any one of claims 1 to 8.

12. A method for producing ammonia, comprising the step of reacting nitrogen with hydrogen in the presence of the ammonia synthesis catalyst according to claim 11.

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